Electroencephalic neurofeedback apparatus and method for bioelectrical frequency inhibition and facilitation

ABSTRACT

An improved method and apparatus for displaying and either inhibiting or promoting selected bioelectrical frequencies emitted by a living organism. The method includes the steps of detecting an analog bioelectrical signal, converting the signal to discrete digital signals representing corresponding frequencies and numerically analyzing the digital signals to determine the different bioelectrical frequencies emitted by the organism. Furthermore, a threshold amplitude associated with a selected digital signal can be established an auditory or visual signal can be sent to the organism to indicate whether the bioelectrical frequency under study is within or outside the threshold amplitude. With this information the organism can be taught to inhibit or facilitate the bioelectrical frequency. The apparatus comprises a pair of electrodes, an analog signal amplifier, an analog to digital converter, a selector to select a frequency of interest, a display monitor, and a computer to distinguish the digital signals as different frequencies, display the frequencies, and determine when the frequency is falling inside or outside a predetermined range. Also, a magnetic medium recording device is used to capture data. Finally, a lighting or sounding circuit is used to tell the organism whether the frequency under study is being inhibited or facilitated.

BACKGROUND OF THE INVENTION

The invention relates in general to the reception and processing ofbioelectrical signals from an organism. Furthermore, the inventionrelates to an improved method and apparatus for receiving bioelectricalsignals, processing the signals and signaling back to the organism so asto allow the organism to either inhibit or facilitate a selectedfrequency.

A number of different feedback-type methods and apparatus are knowndating back to as early as 1960. Early studies by several researchersfocused on bioelectrical feedback on persons suffering from hemiplegia,i.e., paralysis of one lateral half of the body resulting from injury tothe motor centers of the brain.

In 1960, A. A. Marinacci and M. Horande investigated neurofeed back withrespect to left-sided hemiplegia. As reported in "Electromyogram inNueromuscular Re-education", Bulletin of the Los Angeles NeurologicSociety, 25: 57-71, 1960, they inserted needle electrodes into theinvolved left arm muscles, and could find no voluntary nerve impulses.Electrodes were inserted into the normal right deltoid to show thepatient how muscle activity could produce auditory feedback. Theelectrodes were then inserted into the paralyzed left deltoid muscle.The patient was able to generate from 10 to 15 percent motor actionpotential in a location from which there had been no previous detectableactivity. The same procedure was utilized successfully at other musclesites.

In 1964, J. M. Andrews reported on study utilizing a patient group ofhemiplegics who had electromyogram EMG electrodes inserted in theinvolved tricep muscles as reported in "Neuromuscular Re-education ofthe Hemiplegic with the Aid of the Electromyograph," Archives ofPhysical Medicine and Rehabilitation, 45: 530-532, 1964. Auditoryfeedback was provided as the subjects tried to generate sound andmovement. A five-minute trial period was allowed, and seventeen out ofthe twenty patients showed an increase in motor action potentials.

In 1973, H. E. Johnson and W. E. Garton reported on ten hemiplegicpatients, who utilized EMG practices as an aid in total rehabilitationrather than just the return of voluntary movement as in the Andrewsstudy as discussed in "Muscle Re-education in Hemiplegia by use ofElectromyograph Device", Archives of Physical Medicine andRehabilitation, 54: 320-325, 1973. Five out of ten subjects had enoughimprovement to eliminate leg bracing on the involved side.

In 1974, J. Brudny and others used EMG feedback to treat a group ofthirty-six patients, thirteen of whom had hemiparesis. Brudny, J.Korein, J., Levidow, L. Grynbaum, B. B., Lieberman, A., and Friedman, L.W., "Sensory Feedback Therapy as a Modality of Treatment in CentralNervous Disorders of Voluntary Movement," Neurology, 24: 925-932, 1974.In this study surface electrodes were used instead of inserted needleelectrodes. In two individuals there was no change. In one patient therewas relief from muscle spasticity. In six patients function of theextremity was re-established, and in four cases prehension becamepossible.

Also, in 1974, D. Swaan, P. C. W. Van Wieringer and S. D. Fokkemaexplored EMG feedback of seven patients, four of whom were hemiplegic."Auditory Electromyographic Feedback Therapy to Inhibit Undesired MotorActivity," Archives of Physical Medicine and Rehabilitation, 57:9-11,1974. The subjects taught to inhibit the peroneus longus muscle whilecontracting their quadricep muscle. Conventional rehabilitation methodswere used to suppress the undesirable hyperactivity of the peroneuslongus muscles along with the feedback. No justification was given forreinforcement of the quadriceps and inhibition of the peroneus longus.

In 1975, J. V. Basmajian, C. G. Kukulka, M. G. Narayan and K. Takebecompared EMG biofeedback plus physical therapy with the results ofstandard rehabilitation procedures in cases of ankle dorsiflexionparalysis after stroke repeated in "Biofeedback Treatment of a Foot-DropAfter Stroke Compared With Standard Rehabilitation Techniques: Effectson Voluntary Control and Strength," Archives of Physical Medicine andRehabilitation, 56: 231-236, 1975. The authors claimed that an increasein both strength and range of motion in the biofeedback group was twiceas great as the achievements of the exercise control group. The twogroups of patients were not variably matched. When biofeedback was addedto physical therapy, the mixed variables were not controlled.

In 1976, L. P. Taylor and B. Bongar described the use of electromyometryfeedback for the treatment of cerebrovascular lesion patients inClinical Applications in Biofeedback Therapy, Psychology Press, LosAngeles, Calif., 1976. Patients were taught to inhibit one set ofmuscles while simultaneously facilitating others. For example,inhibition of thumb flexion was attempted while thumb extension wasfacilitated.

In 1979, F. Keefe and K. Trombly utilized EMG feedback to aid ahemiplegic patient judge limb position without being able to see thelimb in "Impaired Kinesthetic Sensation: Can EMG Feedback Help?"Presented at the Proceedings of Biofeedback Society of America, TenthAnnual Meeting, February, 1979 in San Diego, Calif. The patientparticipated in an A-B-A-B withdrawal design to evaluate the effects ofEMG biofeedback on accurate limb positioning. EMG feedback with audiofeedback produced improvement in performance relative to baseline.Withdrawal of feedback produced a decrement in performance, and when EMGfeedback was re-instituted, performance once again improved. The patientwas able to generalize the EMG feedback training to improved functionaluse of the arm.

In 1979, R. Koheil, et al, at the Ontario Crippled Children Centre,developed a Joint Position Trainer to provide precise feedback of limbposition to three hemiplegics. Koheil, R., Mandel, A., Herman, A. andIles, G., "Joint Position Training for Hyperextension of the Knee inStroke Patients: Preliminary Results", presented at the Proceedings ofthe Biofeedback Society of America, Tenth Annual Meeting, February, 1979in San Diego, Calif. The Joint Position Trainer provided feedback ofposition rather than of muscle activity, and incorporated a goniometerattached to a leg cuff with auditory feedback of knee joint angle. Twoof the three patients developed improved gait with increased control ofknee hyperextension.

The results of the techniques involved had limited results because thedifficulty of recognizing particular frequencies generated which couldnot be readily determined, nor could the subject have the ability tocontrol these frequencies.

Other research efforts were conducted specifically upon thosebioelectrical signals emanating from the brain. One of the earlier workswas written in 1966 by T. Mullholland and C. R. Evans who described theuse of alpha waves (approximately 7.5-11.5 Hertz) emanating from thebrain to drive a feedback signal that could be perceived by the testsubject and induce relaxation. Mulholland, T., and Evans, C. R., Nature,211: 1278, 1966. The alpha waves could be controlled to some degree bythe test subject's recognition of a tone or light when alpha waves wereproduced. Similarly, differentiation of particular frequencies ofbioelectrical signal prevented the test subject from readilyacknowledging and either inhibiting or facilitating particularfrequencies.

Other electroencephalograph (EEG) feedback devices are described inpublications by Spunda, J. and Radil-Weiss, T., "A Simple Device forMeasuring the Instaneous Frequency of the Dominant EEG Activity",Electroencephalographic Clinical Neurophysiology, 32: 434, 1972. Thisdevice converted EEG frequencies into voltage levels for analysis usingbandpass analysis. A series of wave form generators were activated bythe flip-flop at each positively directed zero point of the filteredsignal resulting in a voltage level corresponding to the frequency.

Another EEG feedback device was described in Hicks, R. G., and Angner,E., "Instrumental evaluation of EEG Time Relationships",Psychophysiology, 6:44, 1970. This device analyzed minute timedisplacements of EEG waves from cortical waves using peak detection anda type of logic as a feedback device.

Also, in Boudrot, R., "An Alpha Detection and Feedback Control System",Psychophysiology, 9:467, 1972, a feedback device picked up alpha wavesand provided auditory and visual stimulus feedback to the patient. Then,in Pfeifer, E. A., and Usselmann, C., "A Versatile Amplitude Analyzerfor EEG Signals to Provide Feedback Stimuli to the Subject", Med. Biol.Eng. 8: 309, 1970, a feedback device analyzed the amplitude and providedfeedback cues to subjects in studies of EEG modification. It allowed forusage with bandpass analysis incorporating logic components and adisplay.

Additionally, U.S. Pat. No. 3,837,331 to Sidney A. Ross, issued Sept.24, 1974, entitled "System and Method for Controlling the Nervous Systemof a Living Organism" describes an apparatus and method for determiningparticular frequencies of a bioelectric signal which is analog bynature. The Ross device like the other devices require the use of bandpass analysis or other techniques to filter out particular frequenciesto study a particular frequency of interest.

In band pass analysis, analog filters analyze how much frequency isproduced in a given period of time, or a frequency in relationship totime and voltage. The apparatus required includes a precisionattenuator, an active band pass filter, a rectifying means and anintegrating means in addition to those components normally utilized inbioelectrical feedback devices. Furthermore, band pass analysis or powerspectral analysis is necessary to isolate the particular frequency ofinterest. Such analysis is typically performed on a large computerrequiring special analytical skills and extensive computing time. Powerspectral analysis looks at the variance of a bioelectrical signal or thecovariance between one or more signal channels. The signal is brokeninto different frequency bands in relationship to the power densitywhich is then analyzed using a fourier series program.

Not only is the above approach burdensome and time consuming, but alsoinaccurate. The frequency results are often distorted because theanalytical approach used is based on exponential and logrithic analysis.Determining the actual frequency desired to inhibit or facilitate is atbest haphazard due to the margins for error in the above approach.

Also, the above referenced devices lack suitable means for displayingand recording the changing frequencies under study for subsequent reviewand manipulation for purposes of analysis. But, most importantly, theseEEG feedback devices lacked the ability to establish selected limits orthresholds in which to gauge the progress of a test subject or rewardthe test subject once the test subject learned to inhibit or facilitatea particular frequency of interest.

The above-mentioned deficiencies are overcome by the present invention.There is a great interest in the neuropsychology and neurophysiologycommunity for such a device which overcomes these deficiencies.Researchers and practitioners should recognize the value immediately ofthe present invention. Furthermore, persons suffering from nervousdisorders, induced by trauma, drug use or cogenital aberration cangreatly benefit from the present invention. The present inventionoperates as a diagnostic tool, as well as, a means for curing nervousdisorders or abnormalities in the body, particularly the brain.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram of a first preferred embodiment ofthe improved method of the present invention;

FIG. 2 is a functional block diagram of a second preferred embodiment ofthe improved method of the present invention;

FIG. 3 is a top right perspective view of a first preferred embodimentof the improved apparatus of the present invention shown associated witha test subject; and

FIG. 4 is a top right perspective view of a second preferred embodimentof the improved apparatus of the present invention shown associated witha test subject.

SUMMARY OF THE INVENTION

The invention includes two embodiments of a method and two embodimentsof an apparatus for practicing the methods, respectively.

The first method is an improved method of detecting and displayinganalog bioelectrical frequencies in an organism's or person's bodycomprising the steps of detecting an analog bioelectrical signal at aselected location in the person's body, amplifying the analogbioelectrical signal, converting the analog bioelectrical signal todigital signals representing particular frequencies, and selecting aparticular digital signal of interest and displaying and/or recordingthe particular signal of interest in the form of a continuous waveformover time.

The apparatus used to perform the above method comprises a receptormeans for attachment to the selected location of the person or organismfor receiving an analog bioelectrical signal, an amplifier foramplifying the analog bioelectrical signal received by the receptormeans and associated therewith, and an analog to digital converter forconverting the analog bioelectrical signal to digital signalsrepresenting corresponding electrical frequencies. The converterreceives the amplified analog bioelectrical signal from the amplifier.

A computer is used for integrating amplitude of one of the digitalsignals over a predetermined duration and dividing a resulting value byvoltage to determine a change in voltage with respect to time duration,and thereby determine electrical frequencies emitted by the person ororganism. The computer then converts the resulting value divided byvoltage to a format which can be plotted over time. A display monitorfor displaying the prescribed format of the corresponding electricalfrequencies can be incorporated.

Furthermore, a magnetic disk recorder for recording the resulting valuedivided by voltage over time is used to record the information forsubsequent review or analysis.

The second embodiment of the method of the invention involves the firstembodiment of the method described above. Additional steps includesending a signal to the person when the particular digital signal ofinterest falls within a selected amplitude threshold for a predeterminedduration, and causing the person to mentally concentrate so as affectthe amplitude of the particular digital signal of interest. This allowsthe person to affect a certain corresponding analog bioelectricalfrequency emitted at the selected location of the person's body.

Subsequent to the step of establishing an amplitude for the particulardigital signal, an additional step may include integrating the amplitudeof the selected digital signal with respect to duration and dividing bythe amplitude threshold voltage. This yields a determination of whethervoltage of the selected digital signal is changing, and thereby whetherthe corresponding analog bioelectrical frequency is being inhibited oraccentuated.

Also, another step may be added by displaying the selected digitalsignal as a continuous waveform and displaying the voltage thresholds ashorizontal lines associated with the continuous waveform to facilitatethe determination of whether the corresponding analog bioelectricalfrequency is being inhibited or facilitated.

Similarly, a step of recording may be added where the digital signalsare recorded to a magnetic medium for review and data manipulation.

The step of continuously displaying the particular digital signal ofinterest as a waveform changing with respect to time can be incorporatedwherein the amplitude threshold voltage is displayed as a straight line.

A step of suppressing exteraneous signals unrelated to the analogbioelectrical signal of interest ma be used to suppress unwanted noise.

The apparatus used in the second embodiment is similar to that apparatusdescribed above. The step of detecting an analog bioelectrical signal isachieved by using two electrodes positioned at the selected location ofthe person's body to be affected. The step of amplifying is achieved byusing a signal amplifier associated with the electrodes and whichrecognizes voltage potential between the electrodes. The step ofconverting is achieved by receiving signals representing voltagevariations over time and using an analog to digital converter to convertvoltage variations into digital pulses.

The step of selecting is achieved using a numerical analyzer to selectdigital pulses corresponding to particular analog bioelectricalfrequencies. The step of sending is achieved by use of a light or soundto the person when the analog bioelectrical frequency recognized betweenthe electrodes falls within a predetermined range for a predeterminedduration. The step of displaying is achieved using a waveform scrollerfor displaying particular digital signals as a continuous wave over timeand using a monitor for displaying the continuous wave over time asplotted by the waveform scroller. The step of integrating is achievedusing a computer which can compute integrals.

Other aspects and advantages of the present invention will becomeapparent from the following description of the preferred embodiments,taken in conjunction with the accompanying drawings, which illustrate,by way of example, the principles of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in the drawings, wherein like numerals represent like elements,an organism 5 can be monitored using a receptor means 7 as shown by theschematics of FIGS. 1-4. The receptor means 7 comprises at least twoelectrodes 9 of a ferrous materials shown attached to a rabbit 11 inFIG. 3 and a man 13 in FIG. 4. The electrodes 9 can be placed on anyportion of the body where bioelectric signals may be of interest. Asshown in FIGS. 3 and 4 the bioelectrical signals of the head 15 of therabbit 11 and the head 17 of the man 13. Voltage potentials between thetwo electrodes 9 can be sensed over time and transmitted by wires 19 toan amplifying means or amplifier 21. One amplifier used is the mendocinomicrocomputer EEG amplifier or equivalent. The amplifier 21 is of a kindthat can amplify analog signals such as bioelectrical signals producedby living organisms. Amplification is necessary because bioelectricalsignals are typically very faint and cannot be readily analyzed byelectrical means. Such amplifiers are commonly known in the art ofelectroencephalographic applications.

Once the analog bioelectrical signal is sufficiently amplified, thesignal can be digitized or demodulated by an analog to digital convertermeans 23 so as to produce discrete digital signals which correspond tothe frequencies inherent in the analog bioelectric signal. Some signalfiltering may be necessary to properly process the analog bioelectricsignal prior to demodulation. Demodulation of the analog bioelectricsignal can be achieved by using a DASH 16 analog/digital input card 25.The input card 25 is manufactured by Metrabyte Corp., and is a highspeed multifunction analog/digital I/O expansion board for a personalcomputer.

The DASH-16 uses an industry standard (HI-674A) 12 bit successiveapproximation converter with a 12 microsecond conversion time giving amaximum throughput rate of 60 KHz in D.M.A. mode. The channel inputconfiguration is switch selectable on the board, providing a choicebetween 16 single ended channels or 8 differential channels with 90 dBcommon mode rejection and ±/-10 v common mode range.

Analog to digital conversions may be initiated in any one of 3 ways, bysoftware command, by internal programmable interval timer or by directexternal trigger to the analog to digital. At the end of the analog todigital (A/D) conversion, it is possible to transfer the data by any of3 ways, by program transfer, by interrupt or by D.M.A. All operatingmodes are selected by a control register on the DASH-16 and are alsosupported by its accompanying utility software.

High input impedance ranges of +1 v, +2 v, +5 v & +10 v unipolar and±/0.5 v, ±/1 v, ±/2.5 v, ±/5 v & ±/10 v bipolar are switch selectable.These ranges are common to all channels and are controlled by the gainof the input instrumentation amplifier. Other ranges may be realizedwith a single user installed resistor. All inputs are multiplexedthrough a low drift, fast settling instrumentation amplifier/sample-holdcombination and the channel input configuration is switch selectable tooperate as either 16 single ended or 8 differential channels.

A 3 channel programmable interval timer (Intel 8254) provides triggerpulses for the A/D at any rate from 250 KHz to 1 pulse/hr. 2 channelsare operated in fixed divider configuration from an internal 1 MHz xtalclock (optional 10 MHz jumper selectable on DASH-16F). The third channelis uncommitted and provides a gated 16 bit binary counter that can beused for event or pulse counting, delayed triggering, and in conjunctionwith the other channels for frequency and period measurement.

2 channels of multiplying 12 bit D/A output. The D/A converters may beoperated with a fixed -5 v reference available from the DASH-16 board togive a 0-+5 v output. Alternatively an external D.C. or A.C. referencemay be used to give different output ranges or programmable attenuatoraction on an A.C. signal. D/A's are double-buffered to provideinstantaneous single step update.

A -5 v (±/0.05 v) precision reference voltage output is derived from theA/D converter reference. Typical uses are providing a D.C. referenceinput for the D/A converters and offsets and bridge excitation to usersupplied input circuits.

Digital I/O consists a 4 bits of TTL/DTL compatible digital output and 4bits of digital input. Apart from being addressed as individual I/Oports, some of the digital inputs do double duty in some modes as A/Otrigger and counter gate control inputs.

The analog/digital input card 25 is incorporated within a modifiedpersonal computer 27 which can be of an IBM PC or XT type sufficient tointerface with the analog/digital input card 25.

The digital signals resulting can be further analyzed with respect tocertain analog bioelectric frequencies sensed. A selector means 29allows sufficient manipulation of the digital signals so as to separateparticular digital signals which correspond to the particularbioelectric analog frequencies to be monitored. This function can alsobe achieved by using the DASH-16 card.

The computer 27 comprises a 8087 numerical processor card 29 with anexpanded memory card 30 which among other things allows the selection ofparticular digital signals of interest corresponding to the bioelectricfrequency to be studied. Such a selection can be performed by digitalseparation using certain digital filters commonly known in the art ofdigital filtering. Many of these techniques can be implemented by use ofthe DASH-16 card.

Furthermore, a computing means 31 is used to integrate the amplitude ofthe particular digital signal over a predetermined duration. Theresulting value is divided by microvoltage to determine a change involtage with respect to time duration, and thereby determine thebioelectric frequencies emitted by the person or animal. Thiscalculation is achieved by the computer 27 driven by particularalgorithms which are herein disclosed and addressed in Appendix Aattached hereto. Appendix A is a list of software variables and theirinterrelationships. The computer 27 with a keyboard 28 then converts theresulting values divided by micro voltage to a format which can beplotted over time. Threshold values can be entered by the keyboard 28and established such that when the amplitude of the resulting signal iswithin a certain amplitude range (the bioelectric signal is within aparticular frequency) a signaling means signals to the person anauditory, visual, or sensible signal indicating that bioelectricfrequencies are within the pre-determined ranges. An amplitude sensingmeans 35 is used which may be a simple algorithm preset or varied by atechnician or the subject coordinating the monitoring.

The signaling means 33 is simply a light box or sound box 37 that emitsa sound or light or series of sounds or lights which indicate to thesubject that the bioelectric frequencies received by the monitoringelectrodes 9 are within a preset frequency range. Of course, thesignaling means can also be any other type of stimuli that can be sensedby the subject. One approach considered is the use of a video type gamedisplaying animations which can be controlled by way of controlling thebrainwave frequencies.

Once the subject is aware that bioelectric frequencies within a certainrange can be sensed, a feedback phenomenon is possible. The subject canbe trained to focus mentally upon obtaining the stimuli from thesignaling means 33 and thereby, alter the bioelectric frequenciesproduced at the location of the electrodes 9. Bioelectric frequencies ofa predetermined kind can either be facilitated and produced more readilyor inhibited once the subject can be alerted to whether thosefrequencies produced are within the preset range.

Furthermore, a suppression means 39 or artifact suppression device canbe used to suppress unwanted signals that would normally trigger thesignaling means 33. Unwanted signals include "noise" attributable tobioelectric activity in the subject's muscles. A bipolar hookup with anear reference may be used incorporating baseline wire 41 connected tothe subject's ear or other part of the body which provides a signal tothe suppressing means 33 which indicates that a comparable signalreceived from the electrodes 9 should be suppressed. The structure andfunction of the suppressed means 39 are commonly known in the art andare not further herein discussed. Suffice it to say that extraneousbioelectric frequencies not of interest emanating from a location notaround the electrodes 9 can be suppressed. As shown in FIG. 4, therequisite suppression circuitry can be found within the amplifier 21 orwithin the computer 27.

A display means 43 or monitor 45 can be used in conjunction with awaveform scroller display card 45 and a graphics display card 46 todisplay the demodulated and processed data resulting from the processedbioelectric signal. The graphics display card is a Hercules monochromecard, but a number of IBM compatible cards can be used. The waveformscroller card 45 is commonly known in the art of computer graphics fordisplaying data points over time on a monitor.

The particular frequency of interest is displayed as a sinosoidal wave48 which changes amplitude depending upon whether the particularfrequency of interest is being inhibited or facilitated. Moreparticularly, the waveform scroller card 47 processes the data receivedby the computing means 31 and displays it on the monitor 45. The actualdata displayed are the values of the integration of the digital signalsof interest over time divided by microvoltage representing theparticular frequencies of interest making up the bioelectric signal.Upper and lower threshold levels can be established and displayed on thedisplay monitor 45 as horizontal lines 49. The horizontal lines 49represent particular microvolt scales correlated to particularbioelectric frequencies. When the amplitude of the sinusoidal waveexceeds the limits imposed by the horizontal lines 49, the signalingmeans 33 or light or sound box 37 send a particular signal to thesubject to indicate that a particular frequency is not being suppressedor inhibited. When the sinosoidal wave 48 is within the horizontal lines49 the subject is sent a different signal indicating that the particularbioelectric frequency of interest is being inhibited at least within themicrovolt levels defined by the horizontal lines 49. Upon practice bythe subject, the horizontal lines 49 can be brought closer togetherrepresenting a requirement that even less of a particular bioelectricfrequency must be produced to achieve a reward response by the signalingmeans. Of course. the use or nonuse of lights or reward systems can bemodified.

A timing means 51 comprising timing circuitry commonly known in the artcan be used to time the required duration that the level of bioelectricfrequency production must stay within proscribed limits before a rewardsignal is given. The duration can be lessened once the subject hasimproved his ability to inhibit the production of certain bioelectricfrequencies. Variability of the duration is a feature which allowsgreater clinical and therapeutic customization of the inventiondepending on the particular subject encountered and the level of skilldeveloped by the subject.

A recording means 53 can be used to record to a magnetic medium or harddisk 55, or floppy disk drive 57 to record on a floppy disk (not shown).If a hard disk 55 is used, a hard disk controller card 58 is necessaryand commonly known in the art of magnetic recording medium. The therapysession results displayed on the display monitor 45 can be stored in aformat to be displayed and compared with past sessions or to be comparedwith future sessions. A large variety of software tools commonly knownin the art of statistical evaluation to compare the subject's progressin inhibiting or facilitating particular bioelectric frequencies can beused. Most helpful is compressing the waveform produced over the entiresession to a format which can be viewed in its entirety on a screen orpage of paper. Such analysis is helpful to see the subject's ability toinhibited or facilitate a particular frequency over the period of theentire therapy session. This information is not only helpful to theclinician, but also to the subject since the cognitive effect on thesubject may enhance his or her ability to further facilitate or inhibitcertain bioelectric frequencies.

Although feedback is primarily provided to the subject by the signalingmeans 33, the display means can be used by the subject to monitor hisown progress in facilitating or inhibiting certain bioelectricfrequencies.

Also, as shown in FIGS. 1 and 3, the invention can further be usedwithout a feedback or signaling means 33 simply to accurately and easilymonitor certain selected bioelectric frequencies from an organism 5 orrabbit 11 as shown. It should be indicated also, that a number ofdifferent EEG type channels can be feed into the invention for purposesof monitoring various areas provided the proper software and hardwaremodifications are adapted as known in the art of EEG monitoring andrecording. A large number of cables, plugs, and jacks necessary forproper operation of the invention are not herein described as thoseaccessory items are commonly known in the art of data processing with amicrocomputer.

The software to be used operates with respect to the parameters asdescribed below and as embodied in Appendix A, as well as with thehardware described. Those skilled in the art will find the followingconsiderations helpful.

Data collection by the software allows wrap-around in its storage, sothere can be no meaning assigned to > or < in comparison of thepointers. Only == or != are useful comparisons.

Data collection proceeds continuously whenever the system is enabled.The pointer "ad₋₋ ptr" always points to the next storage location to beused. This pointer is incremented by the interrupt handler, and is neverchanged by others except at the start of data collection, when it is setto the start of raw data memory.

Data filtering also proceeds continuously under most circumstances. Thepointer filtered always points to the next datum to be applied to thefilters. It is incremented by the collar of the filter programs, and isnever changed by others except at the start of data collection or thestart of data review.

Plotting may be started, stopped, reversed, restarted, etc. Two pointersare involved:

(1) "plotted", which points to the next datum to be plotted; and

(2) "plotptr", which is updated by interrupt service to indicate that itis time to plot another point when plotting at normal speed. Thesepointers are incremented or decremented according to plotting direction:"int runn" is +1 for forward plotting, -1 for reverse, and 0 for forstopped. Thus adding "runn" to the pointer changes it appropriately.

There are a number of points to considering in constructing the program:setting up a patient file, connection to the patient, starting theprogram, and running the program.

Setting Up a Patient File

An example of a patient file is shown below. New files may be createdand edited with a test editor which can be incorporated with the system.The example file contains notes about the file contents. When a newpatient file is being set up these notes can be erased from the newfile.

EXAMPLE

c:/adinp/adcoef

20 100 Raw data trace scale and artifact suppression level

20 30 Middle trace scale and threshold

20 20 Bottom trace scale and threshold

Notes:

The patient's name must appear as the first line of this file.

adcoef names a file where filter coefficients are to be found. It MUSTappear as the second line of this file. scale and artifact suppressionlevel must be in line 3. scale and threshold for the middle trace mustbe in line 4.

scale and threshold for the bottom trace must be in line 5.

Any other notes may be placed later in this file, and the file can thenbe read by the DOS command:

    type patient

Notes can be added by use of any word processor that produces cleanASCII files, but not such as wordstar.

Starting the Program

If the computer is off, open the floppy disk drive 57 and turn the poweron. The computer 27 will go through an elaborate self-testing program;then it will look to drive A: to see if it can read a disk there. If thedoor is open, it cannot read from drive A: so it will read the harddisk, drive C:. It will go through some more testing and loading, andfinally it will show the DOS "prompt" on the screen.

C>

Insert a patient's existing disk, or create a new one, in drive A: andclose the door. Type "EEG" at the keyboard and follow it with the"Enter" key.

The program can be loaded from the hard disk 55, and a file called"patient" on the floppy disk can be read. If that file is not found, theprogram will quit with a message stating: "Cannot find patient file."

If the necessary file is there, a display will indicate the same. Thedisplay shows the name of the patient file on line 12. This normallycomes from disk drive A, so it will show: "a:patient opened.", but thesystem can also be set up to take the file from drive B or C, or asubdirectory of C.

The name of the patient appears on line 14 of the display, and belowline 14 is scaling information and the name, size and date of the lastfile saved on the disk. Then, the display shows the name of the new filethat will be created if you save data resulting from current session,and indicates how much more data can be placed on the disk.

The program then asks whether the information shown is correct. Aseparate disk for each patient, and often several disks for one patientis advisable.

If you answer yes by typing "Y", the computer 27 will go on to load moreinformation and display a menu. If you answer "N" (or any other key) theprogram will allow you to change the disk or switch to a different driveor to quit.

RUNNING THE PROGRAM

The numbers representing "raw input", "low pass filtered input", and thethree displayed values "top", "mid" and "bot", have multiple scalingfactors applied either inherently or by intention. Below are theserelationships.

Inputs in can be defined as follows: "raw"=completely raw input to theamplifier, measured in microvolts. "sig"=signal value afteramplification, analog/digital conversion, conversion to 16 bit twoscomplement notation and low pass filtering. "Sig" is in arbitrary units,and `sig` numbers will generally be larger than the corresponding numberof microvolts Sig is stored in memory and is applied to the 4-7 Hz andto the 12-15 Hz filters, which are referred to here as the middle andbottom filters.

Outputs can be defined as follows:

"top"=deflection of the top trace in response to "sig".

"mid"=deflection of the middle trace in response to the output of themiddle filter when a steady state in-band signal of amplitude sign isapplied.

"bot"=deflection of the bottom trace in response to the output of thebottom filter when a steady state in-band signal of amplitude sign isapplied.

Scaling is important and described below. Because the middle and bottomfilters may be changed and scaling may be changed, and the new filtersand scales may be applied in review of existing data, it is convenientto perform scaling as part of the filtering process. Therefore, "mid"and "bot" are generated directly from the filters, ready for display, sowe can also define:

"mid"=output of the middle filter with "sig" as an input.

"bot"=output of the bottom filter with "sig" as an input.

It is undesirable to alter the values of the original data by scaling.Therefore, the output of the low pass filter, "sig", is separatelyscaled immediately before plotting, converting it from microvolts to atrace deflection measured in pixels.

Scaling factors must be properly set. Scaling occurs, in part as a sideeffect of other functions, such as signal amplification, analog todigital conversion and filtering, and in part because the systemoperator chooses to set a scale for convenience in viewing.

The detailed system design is concerned with trace deflection measuredin pixels, but the system operator is more comfortable thinking about ascale in terms of microvolts per centimeter, or some other grid unit.Therefore, a relationship is established as follows: "grid"=the numberof pixels corresponding to the scale chosen by the user. A likely valueis 20, so that if the user selects a scale of 50 microvolts, then asignal deflection of 50 microvolts will generate a plot deflection of 20pixels.

The computer 27 provides for input of three scaling values from thepatient file or by manual operation during a run. (The operator pressesthe `F4` key and then enters three numbers.) These values are identifiedas: "iscale[top]", "iscale[mid]", "iscale[bot]" which are signal levelsin microvolts representing a deflection of `grid` pixels on the displaymonitor 45.

Note that with a given signal, a large "iscale" generates a smallerpicture. The relationship is that a trace on the monitor 45 for exampleof two grid units in height represents a signal of 2 "iscale"microvolts.

Other arbitrary scaling factors can be used. In order to achieve thedesired scaling on the display monitor 45, in the face of other scalingfactors that are not fully known or understood, a set of factors (oneeach for "top", "mid" and "bot") is chosen experimentally that willachieve the desired result. These values are related to the amplifier21, the selector means 29 and possibly some other factors, but all areindependent of the operator and the patient, so they are stored in afilter coefficient file and are not subject to change by the operator.They relate the arbitrary `sig` units stored in memory to true microvoltmeasurements, and are called (in the computer program) "fullscal[trac]".Therefore:

    microvolts=sig/fullscal[trace].

If the scale chosen by the operator is equal to the grid size, then onepixel will correspond to one microvolt. If the operator chooses adifferent scaling, it must be applied as well. ##EQU1##

Several factors for the top trace are combined into a signal factor. Forconvenience this factor is stored in the coefficient array.

    coeff[top][16]=grid/(iscale[top]*fullscal[top])

so that the multiplication in the plotting program is: ##EQU2## The"fullscal[trace]" values for the middle and bottom traces contain thesame relationship of `sig` units to microvolts and also compensate forgain of the filters. As above, the grid size and the operator selectedscaling are combined with "fullscal[trace]" into a single factor. Forconvenience this is stored in the filter coefficient array as:

    coeff[trace][16]=grid/(iscale[trace]*fullscal[trace]

These factors are applied to the datum (in `sig` units) at the filterinputs so that the filter output is directly in pixels.

Thresholds must be established for the system. Each of the traces has anassociated threshold value which leads to a decision: clamping of thefilters in the case of the top trace, inhibition of the middle trace andreward of the bottom trace. Therefore, "thresh[top]", "thresh[mid]","thresh[bot]" and decision values in microvolts, i.e., input frompatient file and displayed as numbers.

For the top trace, the actual decision is based on the signal levelstored in the memory in the arbitrary `sig` units. Therefore, the toptrace's microvolt threshold is converted to these units by:

    sigthres=thresh[top]* fullscal[top]

For the other traces the decision is based on the filter outputs, whichare already in pixels, so the microvolt thresholds are converted topixels by:

    m.thres=thresh[mid]* grid/iscale[mid]

    b.thres=thresh[bot]* grid/iscale[bot]

A similar conversion is made on the top trace threshold for the purposeof graphic display of the threshold.

    topthres=thresh[top]* grid/iscale[top]

These calculations of thresholds and scaling factors are made in thefunction `chscale()` which are part of the module `thrhold.c`.

Reward logic of the program is critical to proper operation. The digitalfilters in "philtre.asm" generate two values: "bottom.led" and"middle.led", representing the integrated amplitude of the filteredsignal divided by the threshold set for that signal. (Thus a number>1.0means that the signal is greater than the threshold.) Indicator lightsof the signaling means 33 and a counter (not shown) depend on these twovalues. A counter can be used to keep track of the number of times thesubject has been rewarded over the test period.

Three indicator lights 38 may be provided in addition to the counter:they are referred to as red, yellow and green. Red is the inhibitindicator controlled by the undesired frequency through the 5 Hz filterand the variable "middle.led". Yellow is the enhance indicatorcontrolled by the desired frequency. The green light signals that areward is being posted to the counter.

The red light is turned on if "middle.led" is greater than 1.0,indicating that the 5 Hz signal exceeds the threshold. Actually,"middle.led" must become greater than 1.0 by some fixed increment toturn the red light on, and less than 1.0 by the same amount to turn theindicator off. At exactly 1.0 or very close to that value the indicatordoes not change. This will reduce flickering of the indicator.

The yellow light is continuously variable. Its brilliance isproportional to: ##EQU3## which is equal to "bottom.led"=-1.0.

The yellow light is lighted independently of the 5 Hz inhibit signal.Both lights, however, will go off if a muscle or eye blink artifact isdetected, because the inputs to the filters are clamped for one secondupon detection of the artifact as part of the suppression means 39.

The green light signals a reward. When the yellow light is oncontinuously for 0.5 second during which the red light is off, then thegreen light is turned on. An audible signal is given, and the counter isincremented. The green light stays on for 0.5 second and is then, offuntil the next reward. The program allows time setting an interval afterone reward before the next one can start to be earned, so that thefrequency of rewards can be limited if desired.

Obviously, the approach described herein can be greatly modified by theclinician or the subject

It should be appreciated for the foregoing description that the presentinvention provides an improved, more simplistic, more accurate, and lesstime intensive monitoring and/or control of particular bioelectricfrequencies of organisms. The apparatus of the invention can beassembled from components readily available and easily assembled.Furthermore, diagnostic evaluation and patient use is greatly improved.Furthermore, the use of power spectral analysis and analog active bandpass signal filtering can be eliminated.

Although the present invention has been described in detail withreference only to the presently-preferred embodiments, it will beappreciated by those of ordinary skill in the art that variousmodifications can be made without departing from the invention.Accordingly, the invention is limited only by the following claims.

I claim:
 1. An improved apparatus for inhibiting or producing analogbioelectrical signal frequencies in a person's body comprising:(a)receptor means for attachment to the person's body at a locationemitting an analog bioelectrical signal of interest; (b) amplificationmeans for amplifying said analog bioelectrical signal received from saidreceptor means, said receptor means conveying said analog bioelectricalsignal to said amplification means; (c) analog to digital convertermeans for converting said analog bioelectrical signal to digital signalrepresenting particular analog frequencies, said analog signal havingbeen amplified is converted to discrete digital signal representingcorresponding analog frequencies; (d) selecting means to select aparticular digital signal, said selecting means including a numericalanalyzer receiving said discrete digital signals allowing the selectionof a particular digital signal corresponding to a particular analogbioelectrical frequency to be inhibited or accentuated and avoiding thedelay and distortion of power spectral and bandpass analysis; and (e)sensation means for giving the person a particular sensation when saidparticular digital signal is maintained within predetermined ranges ofamplitude for a predetermined duration, thereby allowing the person tomentally concentrate so as to inhibit or produce said particular analogbioelectrical signal frequency which can be acknowledged by the personwhen the person receives said sensation.
 2. An improved apparatus asclaimed in claim 1, further comprising an integrating means forestablishing said predetermined amplitude ranges for a predeterminedduration, wherein said means integrates the amplitude of said particulardigital signal with respect to duration and divides a resulting value bya pr®determined amplitude threshold voltage, thereby allowing thedetermination of whether voltage of said particular digital signal ischanging, and thereby whether said corresponding bioelectrical signalfrequency is being inhibited or accentuated.
 3. An improved apparatus asclaimed in claim 2, further comprising a monitor means for displayingsaid discrete digital signals as a waveform changing with respect totime and displaying said predetermined amplitude ranges.
 4. An improvedapparatus as claimed in claim 3, further comprising a recording meansfor recording said digital signals to a magnetic medium for review anddata manipulation.
 5. An improved apparatus as claimed in claim 4,further comprising a suppression means for suppressing unwanted signalsreceived by said receptor means which can be selectively set to preventsaid unwanted signals received by said receptor means from activatingsaid sensing means.
 6. An improved apparatus as claimed in claim 5,wherein said receptor means comprising two electrodes associated withsaid amplifications means, said analog to digital converter meanscomprising an analog/digital input card which receives said amplifiedanalog bioelectrical signal, said integrating means comprising anumerical processor card which receives said digital signals andprocesses said signals to represent changing voltage over time.
 7. Animproved apparatus for displaying electrical frequencies at a desiredlocation of an organism, comprising:(a) receptor means for attachment tothe desired location of the organism for receiving an analogbioelectrical signal; (b) amplification means for amplifying said analogbioelectrical signal received by said receptor means and associatedtherewith; (c) analog to digital converter means for converting saidanalog bioelectrical signal to digital signals representingcorresponding electrical frequencies, said converter means receivingsaid amplified analog bioelectrical signal from said amplification meansand associated therewith; (d) computing means for integrating amplitudeof one of said digital signals over a predetermined duration anddividing a resulting value by voltage to determine change in voltagewith respect to time duration, and thereby determining electricalfrequencies emitted by the organism, said computing means thenconverting said resulting value divided by voltage to a format which canbe plotted over time while avoiding distortions or delay which occurwith power spectral and bandpass analysis; and (e) display means fordisplaying said resulting value divided by voltage in said format forviewing of said corresponding electrical frequencies.
 8. An improvedapparatus as claimed in claim 7, further comprising a recording meansfor recording said resulting value divided by voltage over time forsubsequent review.